150 PROCEEDINGS OF THE ACADEMY OF 



Erisocrinus conoideds, M. & W. 



Body small, below the summit of the first radials obconic, nearly twice as 

 wide as high ; basal pieces a little wider than long, pentagonal as seen pro- 

 jecting beyond the column, and forming together a small low cup with di- 

 verging sides ; subradials near three times as large as the basal pieces, a little 

 wider than long, and all hexagonal ; first radial pieces half as long as wide, 

 about twice as large as the subradials, and all broadly truncated on the same 

 horizontal plane above, for the reception of the second radial pieces. Surface 

 smooth ; sutures linear, not impressed ; plates not convex. Column and all 

 the parts above the first radial pieces unknown. 



Height to summit of first radials, 0-20 inch ; breadth of do. 0-34 inch. 



This species will be at once distinguished from young specimens of the last 

 of its own size, by its obconic, instead of basin-shaped cup. From Prof. Ko- 

 ninck's species cometa (in case our species should really belong to his genus) 

 it will be distinguished specifically by the less convex outline of the sloping 

 under sides of its cup, as well as by its shorter and proportionally wide first 

 radial pieces. It will of course have to take the name P.hilocrinus conoideus, 

 in case Prof. Koninck's species should prove generically identical with these 

 American forms. 



Locality and position. Springfield, 111., Coal Measures. 



Erisocrinus tuberculatus, M. & W. 



Although we only know this fine species from its detached plates, these 

 agree so exactly in form with the corresponding parts of our Erisocrinus typus 

 from the same beds, that scarcely a doubt can be entertained in regard to 

 their belonging to the same genus ; while they differ so remarkably in their 

 surface characters as to be distinguished at a glance, specifically, from that or 

 any other Crinoid known in our Coal Measures. This difference consists in 

 their entire external surface being covered with regularly disposed, narrow, 

 prominent tubercles, instead of being smooth. 



Of these tubercles there are, on a first radial plate measuring 0-00 inch in 

 breadth and - 54 inch in height, about thirty in number, arranged so as to 

 form two rows of about eight each, ranging parallel to the inferior sloping 

 margins, and one row of about eight along the superior margin. Between 

 this latter row and those below, there are usually a few tubercles either iso- 

 lated or forming a third transverse row. There is likewise usually one or 

 several others at the lower middle angle outside of the regular rows. This 

 arrangement of the tubercles into rows is not, however, always obvious at a 

 first glance, but a tendency to such a disposition can always be seen. 



On the second radials the tubercles are arranged in a single row along the 

 lower and eachaeuperior sloping margin, with one or more in the middle be- 

 tween the rows. In the articulating, or connecting surfaces of the radial 

 plates, we observe no differences between these pieces and those of the corre- 

 sponding parts of E. typus. 



Some of the plates indicate a transverse diameter of 1*40 inch for the entire 

 body. 



If our proposed genus Erisocrinus is, as we have suspected, identical with 

 Pkilocrinus of Koninck, the name of this species will have to be written Pliilo- 

 crinus tuberculatus. 



Locality and position. Upper Coal Measures. Sugar Creek, Sangamon Co., 

 111., and near Brighton, Jersey Co. 



Genus CYATHOCRINUS, Miller, 1821. 

 Cyathocrinus quinquelobus, M. & W. 

 Body broad baain-shaped, composed of very thick, strong plates ; height to 



[Aug. 



